Scientists identify source of fast radio burst in Milky Way

Scientists have solved a mystery on what causes powerful but fleeting radio bursts that zip and zigzag through the universe. Astronomers have had as many 50 different theories for what causes these fast radio bursts. 

On April 28, a super magnetized stellar remnant known as a magnetar blasted out a simultaneous mix of X-ray and radio signals never observed before. The flare-up included the first fast radio burst (FRB) ever seen from within our Milky Way galaxy and shows that magnetars can produce these mysterious and powerful radio blasts previously only seen in other galaxies.

What is a fast radio burst?

Fast radio bursts (FRBs) are intense, millisecond-long bursts of radio waves. First discovered in 2007, their short-lived nature makes it particularly challenging to detect them and to determine their position on the sky.

How was it observed?

This year, on April 27, two space observatories — the Neil Gehrels Swift Observatory and the Fermi Gamma-ray Space Telescope — detected multiple bursts of X-ray/γ-ray emissions coming from the magnetar called SGR 1935+2154. On the following day, the same region of the sky was in view of ground-based telescopes in the Western Hemisphere. 

Two radio telescopes — the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Survey for Transient Astronomical Radio Emission 2 (STARE2), in the United States — detected an FRB from that sky region. The FRB has since been named FRB 200428.

FRB 200428 is the first fast radio burst for which emissions other than radio waves have been detected, the first to be found in the Milky Way, and the first to be associated with a magnetar. It is also the brightest radio burst from a magnetar that has been measured so far — which potentially solves a key puzzle in this field. 

This burst in less than a second contained about the same amount of energy that our sun produces in a month, and still that’s far weaker than the radio bursts detected coming from outside our galaxy. 

Scientists think these are so frequent that they may happen more than 1,000 times a day outside our galaxy. But finding them isn't easy.

What is a magnetar?

A magnetar is a type of isolated neutron star, the crushed, city-size remains of a star many times more massive than our Sun. What makes a magnetar so special is its intense magnetic field. The field can be 10 trillion times stronger than a refrigerator magnet and up to a thousand times stronger than a typical neutron star’s. This represents an enormous storehouse of energy that astronomers suspect powers magnetar outbursts.

The radio burst was thousands of times brighter than any radio emissions from magnetars in our galaxy.

In addition, the radio pulse arrived during an X-ray burst, something that has never before been seen in association with FRBs. Taken together, the observations strongly suggest that SGR 1935+2154 produced the Milky Way’s equivalent of an FRB, which means magnetars in other galaxies likely produce at least some of these signals.

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